Pump Arrangement

ABSTRACT

A pump arrangement comprising at least one first pump and at least one second pump that can be connected or is connected in series behind the first pump. The pump arrangement has a simple construction, lowest possible pump capacity requirements, and quickly establishes a required pressure or vacuum pressure. This is achieved in that a pump capacity of the first pump or a sum of the pump capacities of the first pumps is much greater than a pump capacity of the second pump and that a bypass with a first overflow valve is connected between the first pump and the second pump.

CROSS REFERENCE

This application claims priority to German Patent Application No. 10 2013 108090.1, filed Jul. 29, 2013, which is hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a pump arrangement comprising at least one first pump and at least one second pump that can be connected or is connected in series behind the first pump.

BACKGROUND

Pump arrangements are known and used to generate high pressures or rough to ultra-high vacuums. They are described, e.g., on the German Wikipedia page, www.de.wikipedia.org, keyword “Vakuumpumpe (vacuum pump),” section “Erzeugung eines Ultrahochvakuums (generating an ultra-high vacuum).” According to this page, mechanical vacuum pumps are used to first generate a fore-vacuum and then turbomolecular pumps are used to generate an ultra-high vacuum.

The terms “pump” and “vacuum pump” comprise, in the sense of this invention, both the actual pump and also possibly a pump chamber formed in this pump. The term “pump chamber” is here defined as one of several chambers inside of a compression chamber.

For example, vacuum pumps are used in motor vehicles to provide brake boosters with vacuum pressure. Known here are vacuum pumps with corresponding pump capacity or vacuum pumps connected in series; these known arrangements have the disadvantage that the required pressure or vacuum pressure is established only relatively slowly and/or a relatively large pump capacity is required.

The problem of the invention is therefore to create a pump arrangement that has a simple construction, the lowest possible pump capacity requirements, and can quickly establish a necessary pressure or vacuum pressure.

SUMMARY OF THE INVENTION

A pump capacity of the first pump or a sum of the pump capacities of the first pumps is much greater than a pump capacity of the second pump and a bypass with an overflow valve is connected between the first pump and the second pump. In this way, a predetermined chamber can be quickly evacuated; air that is suctioned from the at least one first pump and cannot be output by the at least one second pump flows via the bypass and the overflow valve into the surroundings. In this way, a greater pump capacity of the first pump(s) can be fully utilized, without being limited by the smaller pump capacity of the second pump(s). Therefore, a predominant part of the volume to be output is pumped in a very short time and a predetermined desired vacuum pressure is quickly established. When a predetermined vacuum pressure is reached in a connecting line between the first and the second pump, the overflow valve automatically closes, e.g., due to the pressure difference between the surroundings and the interior of the connecting line. Only then are the first and the second pumps connected completely in series, which causes the further reduction in pressure down to the desired vacuum pressure. This also happens very quickly due to the low volume still to be output.

In one construction, a suction side of the second pump is connected to a line that comprises a second overflow valve and a switchable valve is arranged between the first pump and the second pump. In this way, all pumps can be initially operated in parallel, so that the majority of the volume to be output can be pumped even more quickly.

In another construction, the overflow valve is a check valve. This has a mechanically simple construction, is reliable, and operates automatically.

In another construction, the switchable valve between the first pump and the second pump is a choke. This valve automatically and mechanically switches at a preset differential pressure of, e.g., 200 mbar.

Alternatively, the valve can be switched electrically. In this way, the control of the pump arrangement can be integrated into an overall control.

Alternatively, the valve can be controlled by differential pressure. This can be produced relatively easily and economically.

In another construction, additional pumps are connected in series, wherein a bypass with an overflow valve is connected between each pair of pumps formed adjacent in series. In this way, even larger pressure differences can be achieved with quicker evacuation.

The claims are explained using the example of vacuum pumps. For a pump arrangement for generating over-pressure, the statements above apply accordingly.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made more particularly to the drawings, which illustrate the best presently known mode of carrying out the invention and wherein similar reference characters indicate the same parts throughout the views.

FIG. 1 is a first pump arrangement with one first pump and one second pump,

FIG. 2 is a second pump arrangement with three first pumps,

FIG. 3 is a third pump arrangement with an electrically switchable valve,

FIG. 4 is a membrane valve as an example of a pneumatically switchable valve,

FIG. 5 is a sixth pump arrangement with pneumatically switchable valves, and

FIG. 6 is curve for the pressure profile as a function of time.

DETAILED DESCRIPTION OF THE DRAWINGS Example 1

As can be seen from FIG. 1, a first pump arrangement of a first embodiment comprises a first pump 1, a second pump 2, and a bypass 3 with a first overflow valve 4. The pumps 1, 2 are constructed as vacuum pumps and equipped with electric motors as a drive, wherein the first pump 1 has a much larger pump capacity than the second pump 2.

The first pump 1 is connected on the suction side to a container 5, e.g., a brake booster, to be evacuated, in which a predetermined pressure range (vacuum pressure) is to be maintained during operation. The second pump 2 is connected in series to the first pump 1, that is, it is connected on the suction side to a pressure side of the first pump 1. The bypass 3 in which the first overflow valve 4 is arranged is connected to a connecting line between the pumps 1, 2 parallel to the second pump 2. The first overflow valve 4 is constructed, e.g., as a check valve 4.

The pump arrangement is arranged, e.g., in a motor vehicle, in order to provide a brake booster with a required vacuum pressure. The container 5 is then constructed as the brake booster.

The pumps 1, 2 are connected via a control device to a voltage source.

When the motor vehicle is in operation and the drive motor starts, the electric motors of the pumps 1, 2 are supplied with power via the control device, so that they suction air from the container 5. In this way, the first pump 1 outputs much more air than the second pump 2 can receive and forward on the suction side, so that an over-pressure is generated in the connecting line. This has the effect that the overflow valve 4 opens, so that the air that is not output from the second pump 2 can flow out into the atmosphere. Therefore, in a very short time, a predominant part of its air contents are suctioned from the container 5 until, due to the developing vacuum pressure in the container 5, the pressure in the connecting line drops so much that the overflow valve automatically closes. In this way, the pumps 1, 2 are connected completely in series, so that a stronger vacuum (lower absolute pressure) down to a desired value can be established.

Optionally, the control device is constructed such that the second pump 2 is supplied with power offset in time relative to the first pump 1. Furthermore, the pump arrangement can be equipped with at least one pressure sensor that allows a control of the pumps 1, 2 as needed and thus an economical operation, e.g., at a lower switching pressure and an upper switching pressure of the vacuum pressure.

Example 2

A second embodiment is shown in FIG. 2 and differs from the first by the following:

A plurality of first pumps 1, here three, are connected in parallel. The bypass 3 with the overflow valve 4 is connected to the common pressure line of the first pumps 1 before the second pump 2.

The pumps 1, 2 and especially the first pumps 1 are advantageously identical.

Example 3

A third embodiment is shown in FIG. 3 and differs from the first by the following:

A suction side of the second pump 2 is also connected to the container 5, wherein a second overflow valve 6 is installed in an associated suction line. This advantageously has an identical construction as the first overflow valve 4 and is arranged so that it does not affect the connection of the suction side to the first pump 1 and it automatically closes when the pressure in the suction line is greater than in the container 5.

Furthermore, a valve 7, e.g., a magnetic valve that causes the open/close functions, is arranged between the pumps 1, 2. The valve 7 can be actuated here by a control device 8, e.g., as a function of a pressure in the container 5. A pressure sensor 9 is arranged on the container 5 for the continuous determination of this pressure.

When the motor vehicle is in operation, both pumps 1, 2 are always turned on or off simultaneously. If a pressure in the container 5 exceeds a predetermined upper limit, the valve 7 is electrically closed by the control device 8. In this way, the two pumps 1, 2 operate in parallel, so that the second pump 2 also suctions the container 5 via the suction line and therefore this container is evacuated more quickly. The second overflow valve 6 is here opened automatically.

The second overflow valve 6 closes automatically under predetermined pressure conditions.

As soon as a lower limit of the pressure is reached in the container 5, the control device 8 opens the valve 7, so that the two pumps 1, 2 are now connected in series and a stronger vacuum pressure can be generated in the container 5.

The two pumps 1, 2 remain in operation until a lower predetermined switching pressure is reached in the container 5; the pumps 1, 2 are then switched off by the control device 8, etc. When an upper predetermined switching pressure is reached in the container 5, the pumps 1, 2 are switched on again. In this way, the necessary vacuum pressure between the two switching pressures is guaranteed.

Example 4

A fourth embodiment relates to a pneumatic control of the valve by means of differential pressure using the example of a membrane valve 10. It differs from the first embodiment by the following:

A suction side of the second pump 2 is also connected to the container 5, wherein a second overflow valve 6 is installed in an associated suction line. This advantageously has an identical construction as the first overflow valve 4 and is arranged so that it does not affect the connection of the suction side to the first pump 1 and it automatically closes when the pressure in the suction line is greater than in the container 5.

The membrane valve 10 that is shown in FIG. 4 in detail is also arranged in the connecting line between the pumps 1, 2.

The membrane valve 10 comprises a housing 11 that is divided by a membrane 12 into a separating chamber 11 a and a work chamber 11 b. An inlet tube 13 and an outlet tube 14 are connected to the separating chamber 11 a, wherein the inlet tube 13 is connected to the pressure side of the first pump 1 and the outlet tube 14 is connected to the suction side of the second pump 2. A control tube 15 is connected to the work chamber 11 b and to the container 5. A spring 16 is pretensioned against the membrane 12 so that when there is an equal pressure in the separating chamber 11 a and the work chamber 11 b, an inner end of the outlet tube 14 is closed by means of a sealing washer 17 mounted on the membrane 12.

When the motor vehicle is in operation, both pumps 1, 2 are always turned on or off simultaneously. As long as a vacuum pressure preset by a spring force of the spring 16 is not reached in the container 5, the outlet tube 14 is closed by the sealing washer 17 due to the spring force acting on the membrane 12, so that the pumps 1, 2 are connected in parallel. The second overflow valve 6 is here opened automatically. In this way, the container is evacuated in the shortest possible time down to the predetermined vacuum pressure. The second overflow valve 6 closes automatically under predetermined pressure conditions.

As soon as the predetermined vacuum pressure is reached and the pressure falls below this vacuum pressure, a force acting on the membrane 12 by the pressure in the separating chamber 11 a is greater than the spring force plus the force acting due to the pressure in the work chamber 11 b. In this way, the membrane 12 moves in the direction of the work chamber 11 b, so that the sealing washer 17 releases the allocated end of the outlet tube 14. Thus, a fluidic connection between the inlet tube 13 and the outlet tube 14 is established. The pumps 1, 2 are now connected in series.

Example 5

A fifth embodiment differs from the fourth by the following:

Instead of the membrane valve 10, a choke is used.

Example 6

A sixth embodiment is shown in FIG. 5 and differs from the fourth by the following:

There is also a third pump 18 that is connected behind the second pump 2—like the second pump 2 behind the first pump 1—to the bypass 3, the overflow valves 4, 6, and the membrane valve 10.

The inclusion of the membrane valve 10 is shown in FIG. 5 also for the fourth embodiment.

The examples are described so that the first pump 1 comprises one or three pumps and the second pump 2 and the third pump 18 each have a single pump. The invention can also be constructed such that the first pump 1, the second pump 2, and the third pump 18 each comprises an arbitrary number of pumps connected in parallel.

Each pump arrangement can be equipped with the pressure sensor 9 and the control device 8 that switches the pumps 1, 2, 18 according to the switching pressures.

A typical (vacuum) pressure profile P of the pump arrangement according to the invention versus time T is shown in FIG. 6 with the typical switching pressures. P1 is here the vacuum pressure at which the pumps 1, 2, 18 are switched from parallel operation to series operation by closing the overflow valves 4, 6 and opening the valves 7, 10. P2 is the upper switching pressure and P3 is the lower switching pressure. As can be seen from the curve profile, for a pump arrangement according to the invention, a required vacuum pressure is achieved in a very short time.

LIST OF REFERENCE SYMBOLS

-   1 First pump -   2 Second pump -   3 Bypass -   4 First overflow valve -   5 Container -   6 Second overflow valve -   7 Valve -   8 Control device -   9 Pressure sensor -   10 Membrane valve -   11 Housing -   11 a Separating chamber -   11 b Work chamber -   12 Membrane -   13 Inlet tube -   14 Outlet tube -   15 Control tube -   16 Spring -   17 Sealing washer -   18 Third pump 

1. A pump arrangement, comprising at least one first pump; and at least one second pump that can be connected or is connected in series behind the first pump, wherein a total pump capacity of the at least one first pump is much greater than a pump capacity of the second pump; and that a bypass with a first overflow valve is connected between the first pump and the second pump.
 2. The pump arrangement according to claim 1, wherein a suction side of the second pump is also connected by means of a line that comprises a second overflow valve to a container to be evacuated and that a switchable valve is arranged between the first pump and the second pump.
 3. The pump arrangement according to claim 1, wherein the over-flow valve is a check valve.
 4. The pump arrangement according to claim 2, wherein the valve is a choke.
 5. The pump arrangement according to claim 2, wherein the valve can be switched electrically.
 6. The pump arrangement according to claim 2, wherein the valve can be controlled by differential pressure.
 7. The pump arrangement according to claim 1, wherein additional pumps are connected in series, wherein a bypass with an overflow valve is connected between each pair of pumps formed adjacent in series. 